Since 1965, the Applicant has been studying the determinants of maternal behavior in the puerperal rat. The present proposal is focused on some of the mechanisms that serve to initiate the behavior and others that serve to maintain it. With respect to the former, we are studying changes in hypothalamic norepinephrine at about the time of parturition. And with respect to the latter, we are studying a pheromonal substance emitted by the maternally-behaving female that serves to attract young. BIBLIOGRAPHIC REFERENCES: Leidahl, L.C. & Moltz, H. Emission of the maternal pheromone in the nulliparous female and failure of emission in the adult male. Physiol. Behav., 1975, 14, 421-424. Moltz, H., Rowland, D., Steele, M., & Halaris, A. Hypothalamic norepinephrine: Concentration and metabolism during pregnancy and lactation in the rat. Neuroendocrinology, 1975, 19, 252-258.